Tubular evaporator



Jan. 5, 1965 A. J. KOCH TUBULAR EVAPORATOR 2 Sheets-Sheet 1 Filed March 11, 1963 f y m Jan. 5, 1965 A. J. KOCH TUBULAR EVAPORATOR 2 Sheets-Sheet 2 Filed March 11, 1963 LS EQHHHHH H H @WQM H @HHMHM Q. H

United States Patent aisasssi Patented Jan. 5, 1965 [ice 3,163,996 TUKEULAR EVAPGRATGR Alan I. Koch, Evansvitle, Ind, assignor to Whirlpool Corporation, a corporation of Delaware Filed Mar. 11, 1963, Ser. No. 264,281} 12 Claims. (ill. s2 27c This invention relates to refrigeration apparatus and in particular to evaporators for use in such refrigeration apparatus.

In one form 'of conventional refrigeration apparatus, refrigeration is efiected by delivering refrigerated air to a refrigeration chamber. In such refrigeration apparatus, the air is conventionally cooled by passage in heat transfer association with an evaporator disposed exteriorly of the chamber and is circulated to and from the chamber by suitable ducts. The present invention comprehends an improved evaporator arrangement for use in such refrigeration apparatus.

Thus, a principal feature of the present invention is the provision of a new and improved evaporator structure.

Another feature of the invention is the provision of such an evaporator structure having a new and improved tubular configuration.

A further feature of the invention is the provision of such an evaporator structure providing a plurality of primary heat transfer means.

Still another feature of the invention is the provision of such evaporator structure providing a plurality of axial flow passages for conducting a fluid to be refrigerated in a plurality of paths.

A still further feature of the invention is the provision of such evaporator structure having new and improved defrost means.

A yet further feature of the invention is the provision of such evaporator structure including a first tubular heat transfer element, a second tubular heat transfer element coaxially within the first heat transfer element, the elements defining a flow passage therebetween, a third heat transfer element extending across the passage and in heat transfer association with the first and second elements, means for conducting fluid refrigerant in heat transfer association with the first and second elements, and means for conducting a fiuid to be refrigerated through the passage to have heat transfer association with each of the elements.

Still another feature of the invention is the provision of such an evaporator structure further including an outer housing defining between itself and the first tubular heat transfer element a second flow passage therebetween.

Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein:

FIGURE 1 is a side elevation of an evaporator embodying the invention;

FIGURE 2 is an end elevation thereof looking from the left of FIGURE 1; and

FIGURE 3 is a diametric section thereof taken substantially along the line 3-3 of FIGURE 2.

In the exemplary embodiment of the invention as disclosed in the drawing, an evaporator generally designated 19 comprises a first tubular heat transfer element 11 and a second tubular heat transfer element 12 coaxially within the first element 11, the elements defining a flow passage 13 therebetween. A third heat transfer element 14 extends across the passage 13 in heat transfer association with heat transfer element 11 and heat transfer element 12. A tubular housing 15 is spacedcoaxially outwardly of the first heat transfer element 11 by means of a plurality of spacers 16 to define a second flow passage 17 therebetween.

More specifically, first heat transfer element 11 comprises a tubular evaporator plate formed of a thermally conductive material which may be formed by conventional roll-bond forming means to define a refrigerant passage is extending concentrically therein. An inlet conduit 19 is connected to one end of the passage 18 for introducing refrigerant fluid into the passage 18 and a connecting por tion Zfi is provided between the opposite end of the passage 18 and one end 21 of the second tubular element 12 for conducting the refrigerant fluid to the interior of the second heat transfer element 12. A delivery conduit 22 is provided at the opposite end of the heat transfer element 12 for conducting the refrigerant fluid from the evaporator it for subsequent recompression by suitable compression means (not shown).

The third heat transfer element 14 herein comprises a plurality of radially extending fins 23. As best seen in FIGURE 2, the fins may be formed from a single sheet of heat conductive material, such as aluminum, by folding the sheet in a serpentine fashion, the length of the individual fins being substantially equal to the spacing between the heat transfer elements 11 and 12 and the fins being interconnected by radially outer connecting portions 24 and radially inner connecting portions 25, the connecting portions 24 and 25 being in intimate heat transfer association with the heat transfer elements 11 and 12, re spectively. In the illustrated embodiment, the heat transfer element 1 2 comprises a tubular member of thermally conductive material force fitted between the heat transfer elements 11 and 12 to provide rigidity to the assembled structure and high efficiency of heat transfer from the heat transfer elements 11 and 12 to the heat transfer element 14.

As shown in FIGURE 2, the flat plans of the respective fins Z3 define axial planes of the evaporator so that a plurality of cylindrical sector flow passage 13a are defined therebetween cumulatively comprising the flow passage 13 through which the air to be refrigerated is circulated. In the illustrated embodiment, the air is circulated from the right end 2% of the evaporator to the left end 27 thereof, as illustrated in FIGURE 3. Thus, the air is in effective heat transfer association during its passage through the evaporator with the outer heat transfer element 11 and the inner heat transfer element 12;, which elements are directly cooled by the passage of the refrigerant fluid 1n direct contact therewith.

The air in passage 13 is further in heat transfer association with the fins 23 which as indicated above are cooled by their heat transfer association with the primary cooling elements, namely the heat transfer elements 11 and 12,

As best seen in FIGURES 2 and 3, the flow passage 17 between housing 15 and first heat transfer element 11 provides a second axial path for passage of air through the evaporator, the air in passage 17 being refrigerated by direct contact thereof with the heat transfer element ll. As the radial dimension of the flow passage 17 is relatively small, a highly efficient refrigeration of the air in the passage is obtained as substantially all portions of the air are caused to impinge substantially directly on the heat transfer member 11 in the course of the flow thereof axially through the passage 17.

As frost may be deposited on the evaporator surfaces during the operation thereof, it is desirable to provide means for periodically removing this frost and thereby maintaining the efiiciency of the evaporator. To this end, an electric heater cable 2% is wrapped around the first tubular element 11 to be disposed within passage 17. The cable is suitably formed so that when electrical current is passed therethrough heat energy is developed therein which is transmitted to the heat transfer member 11. As the heat transfer member 14 and the heat transfer member 12 are in thermally conductive association with throughout the respective heat transfer members to melt frost collected thereupon. To facilitate the removal of the melt resulting from the defIosting operation, the heat transfer member 14 is provided with a plurality of notches 29 adjacent radially outer connecting portions 24 and notches 3t adjacent radially inner connecting portions 25 providing a flow path for the melt adjacent these portions.

In the illustrated embodiment, the tubular heat transfer element 11 is maintained in the tubular configuration by means of a pair of outturned end flanges 31 and 32 secured in face-to-face relationship by suitable means such as screws 33 extending therethrough. The distal ends 34 of the flanges are turned to provide a supporting structure resting on the housing 15 and thereby cooperating with the spacer 16 to retain the force fitted assembly of the heat transfer members 11, 12 and 14 in coaxially centered relationship within the housing 15. As the flange 31 and 32 are formed of the thermally conductive material of which the heat transfer element 11 is formed, further heat transfer is effected between the flanges and the housing 15.

It is believed that from the above description of the evaporator structure a full understanding of the functioning of the apparatus is apparent. However, in brief recapitulation, the evaporator functions in a novel and simple manner to refrigerate a fluid such as air flowed axially through the evaporator and more specificially flowed through the plurality of sector passages 13a cumulatively defining the first air flow passage 13, and through the outer annular passage 17. In passing in heat transfer association with each of the primary heat transfer members 11 and 12 and with the secondary heat transfer member 14, the air in flow passage 13 is refrigerated to the preselected low temperature which may be substantially below 32 F. Further, the air passing through passage 17 may simularly be refrigerated to the desired low temperature by virtue of its improved heat transfer association with the member 11. The refrigerant is delivered firstly through the evaporator passage 18 in the heat transfer member 11 and then through the heat transfer member 12 which effectively defines an accumulator having the lowest temperature of the apparatus whereby improved refrig eration of the air is effected. My virtue of the large area of the heat transfer member 14 resulting from the substantial number of fins of which this member is comprised, improved refrigeration of the air is obtained.

The simple cylindrical configuration of the evaporator permits facilitated use thereof in the modern refrigerator structures such as those utilizing molded-in-plaoe insulation. The tubular configuration provides improved uniform air flow and thus improved efiiciency in heat transfer. As the cooling surfaces within the evaporator are substantially uniformly refrigerated by means of the improved dual primary refrigeration members, improved uniform refrigeration of the air is obtained. The simple arrangement of the evaporator results in extremely low cost and effectively foolproof long life. The improved defrosting means provides positive self-clearing defrosting of the evaporator effectively eliminating the need for additional drain-trough defrosting means.

While I have shown and described one embodiment of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made Without departing from the spirit and scope of the invention as defined in the appended claims. The embodiment of the invention in which an exclusive property or privilege is claimed is defined as follows:

1. An evaporator comprising: a tubular evaporator sheet; a tubular accumulator coaxially within said evaporator sheet, said accumulator and sheet defining a passage therebetween for flow therethrough of a. fluid to be refrigerated; and means for conducting iiuid refrigerant in 42 heat transfer association successively with said evaporator and accumulator.

2. An evaporator comprising: a first tubular heat transfer element; a second tubular heat transfer eiernent coaxially within said first heat transfer element, said elements defining a flow passage therebetween; a third heat transfer element extending across said passage and in heat transfer association with said first and second elements; means for conducting fluid refrigerant in heat transfer association successively with said first and second elements; and means for conducting a fiuid to be refrigerated through said passage to have heat transfer association with each of said elements.

3. The evaporator of claim 2 wherein the means for conducting fluid refrigerant includes means defining a fiow passage integral with said first tubular element.

4. The evaporator of claim 2 wherein the first tubular element comprises a roll bonded evaporator sheet and said means for conducting fluid refrigerant includes refrigerant passages of said roll bonded evaporator sheet.

5. The evaporator of claim 2 wherein said third heat transfer element comprises a plurality of fins formed of a thermally conductive material.

6. An evaporator comprising: a first tubular heat transfer element; a second rectilinear tubular heat transfer element coaxially within said first heat transfer element, said elements defining a flow passage therebetween; a third heat transfer element extending across said passage and in heat transfer conductive association with said first and second elements; means for conducting fluid refrigerant in heat transfer association with said first and second elements; means for conducting a fiuid to be refrigerated through said passage to have heat transfer association with each of said elements; and means in heat transfer association with at least one of said elements for selectively providing heat energy to each of said elements for defrosting said elements.

7. The evaporator of claim 6 wherein the means for defrosting said elements comprises a tube wrapped around the first heat transfer element in heat transfer association therewith.

8. An evaporator comprising: a first tubular heat transfer element; a second tubular heat transfer element coaxially within said first heat transfer element, said elements being disposed to define a horizontal flow passage therebetween; a third heat transfer element extending in an axial plane across said passage and in heat transfer associated with said first and second elements; means for conducting fiuid refrigerant in heat transfer association with said first and second elements; means for conducting a fluid to be refrigerated through said passage to have heat transfer association with each of said elements; mean in heat transfer associated with at least one of said elements for selectively providing heat energy to each of said elements for defrosting said elements; and means for conducting from the evaporator melt resulting from a defrosting of said elements.

9. The evaporator of claim 8 wherein the melt conducting means comprises means defining an opening in said third heat transfer element.

10. The evaporator of claim 8 wherein said melt conducting means comprises a plurality of notches in said third heat transfer element adjacent each of said first and second heat transfer elements.

11. An evaporator comprising: a tubular evaporator sheet; a tubular accumulator coaxially within said evaporator sheet, said accumulator and sheet defining a passage therebetween for flow therethrough of a fluid to be refrigerated; a fin element extending across said passage and in heat transfer association with said sheet and accumulator; and mean for conducting fluid refrigerant in heat transfer association successively with said evaporator and accumulator.

12. An evaporator comprising: a first tubular heat transfer element; a second tubular heat transfer element coaxially Within said first heat transfer element, said elements defining a first flow passage therebetween; a third heat transfer element extending across said passage and in heat transfer association With said first and second elecments; means for conducting fluid refrigerant in heat transfer association successively with said first and second elements; a tubular housing element spaced coaxially outwardly of said first element and defining a second flow passage therebetween; and means for conducting a fluid to be refrigerated through said passages to have heat transfer association with each of said first, second and third elements.

References Cited in the file of this patent UNITED STATES PATENTS Kettering Mar. 10, Campbell 1 May 26, Clerc May 25, Boling Sept. 23, Herndon et a1 June 11, Simmons Jan. 6, Kritzer Sept. 8, Caswell May 9,

Gardner Jan. 1, 

1. AN EVAPORATOR COMPRISING: A TUBULAR EVAPORATOR SHEET; A TUBULAR ACCUMULATOR COAXIALLY WITHIN SAID EVAPORATOR SHEET, SAID ACCUMULATOR AND SHEET DEFINING A PASSAGE THEREBETWEEN FOR FLOW THERETHROUGH OF A FLUID TO BE REFRIGERATED; AND MEANS FOR CONDUCTING FLUID REFRIGERANT IN HEAT TRANSFER ASSOCIATION SUCCESSIVELY WITH SAID EVAPORATOR AND ACCUMULATOR. 